Systems for diagnosing the operating state of a motor vehicle diesel engine are known in the art that use information supplied by systems for acquiring signals associated with the engine, generally comprising systems for acquiring the pressure in the engine cylinders and the engine shaft angle conventionally associated with the Diesel engine, in particular to diagnose leaks from the cylinders thereof.
Strategies for controlling the operation of an engine using a cylinder pressure signal for other engine control functions are also known in the art. Systems using such strategies assume that the acquisition systems are operating correctly and are properly calibrated. Consequently, if at least one acquisition system is faulty, a leak may be diagnosed even though the suspect cylinder(s) are operating satisfactorily, or a malfunction or an increase in pollutant emissions may be caused if the engine management system fails to take account of the fault or drift.
Moreover, in the event of a predetermined fault or drift of the engine or the acquisition systems, the prior art systems referred to above merely deliver a diagnosis for the attention of the user of the vehicle, to enable manual repair or servicing even though, as a general rule, the engine is associated with onboard correction means able to correct such faults and/or drifts.
Additionally, such systems conventionally employ algorithms based on parametric models of the engine or of the changing pressure in the cylinders. Those algorithms generally necessitate a large number of operations, making it difficult to envisage carrying out the corresponding data processing in an onboard computer of the vehicle, which is generally a microcontroller of limited computation capacity.